Wire manufacturers produce electrical wire in long, continuous lengths. The wire is normally wound on spools for sale to wire suppliers or end users, hereinafter referred to, collectively, as customers. It is not uncommon for wire to break during the wire manufacturing process. When this occurs, the manufacturer usually splices the wire back together and the manufacturing process continues. When the breakage of an insulated electrical wire occurs, the manufacturer usually trims back the insulation on either side of the break and welds the two ends of the conductor together. Since it is not uncommon for several breaks to occur during any one production run, there may be several splices on a particular spool of wire, especially a spool containing several thousand feet of wire. An even more common cause of wire splices than breakage is manufacturing problems that occur during insulation application. Extrusion and tape wrapping are examples of manufacturing problems that occur during the application of insulation.
While splices in a spool of wire are common, they are, unfortunately, undesirable and, in some cases, unacceptable to customers because, even though splices provide electrical continuity in the wire, there is an increased likelihood of wire failure at the splices. For this reason, some customers will use only wire lengths that are free of splices. However, because splices have been difficult to identify, splices can be overlooked, and a length of wire containing a splice used in a customer's product. If such a spliced wire is later discovered, the product containing the spliced wire may have to be recalled for repair in order to prevent a later failure of the product. The aircraft industry is one industry in which spliced wires are unacceptable. Many wires used in an aircraft are bundled into wire harnesses for routing through the aircraft. If a spliced wire is inadvertently used in a wire harness, and later discovered, it must be replaced. Obviously the cost of reworking a wire harness is very costly. Perhaps even more significant is the situation where spliced wire is not discovered after it has been installed. A fault caused by a splice in the wire may cause extensive damage to surrounding wires and structures, resulting in costly repairs.
For the reasons noted above, it is of great interest to some customers, such as aircraft manufacturers, that they be able to locate every splice in a spool of wire. In some instances, manufacturers, as an aid to their customers, may attach a label to a spool indicating how many splices exist on that particular spool of wire. However, rarely, if ever, are the locations of the splices provided on the manufacturer's label. To assist a customer in locating each splice as the wire is unwound from the spool, wire manufacturers will sometimes flag splices with colored tape or some other type of marker. Unfortunately, such flagging is unreliable since manufacturers sometimes miss splices and, in any event, do not flag every splice on every spool of wire they sell. Moreover, in some instances manufacturers have used splice markers that are not readily detectable. As a result, in the past, splices have been overlooked by customers, causing great expense when a spliced wire has to be replaced or a product has to be repaired.
In addition, some customers specify an acceptable minimum distance between splices in a spool of wire. In order to provide wire that meets such specifications, a manufacturer must track the location of each splice and provide only wire that meets the customer's specs. Historically, however, customers consistently have received spools of wire with spacings between splices that do not meet their minimum distance requirements. Unfortunately, customers cannot readily verify that wire splice separation distances are within specs because, as noted above, manufactures do not normally provide splice location information.
Also of interest to customers is the ability to verify the actual length of the wire on a spool. Ideally, the actual length of wire on a spool is equal to the length of wire ordered by the customer. Practically, however, there is usually a variation between the actual length of wire on a spool and the length ordered. For customers that purchase large quantities of wire each year, these variations can translate into significant costs. For example, if every spool purchased contained slightly less than the amount ordered, the customer would end up paying for a significant amount of wire that is never actually received. Accordingly, these customers are interested in determining the actual amount of wire on each spool so that any discrepancies can be brought to the attention of the wire manufacturer or supplier.
There exist prior art machines that both measure the length of wire as it is unwound from one spool and rewound on another spool and detect splices in the wire. These machines, however, do not provide this information in a data form that can be easily retrieved by a customer. Rather, these prior art machines require that an operator read a display that gives the running total of the wire length as it advances through the machine. When a splice is detected, the advancing wire is stopped and the operator reads and records the current wire length shown on the display. One problem with these prior art machines is that they rely on an operator to read and record the information and, thus, are subject to operator error. Further, if an operator does not record the information, the information is lost, unless the wire is remeasured. Obviously, manually recording information, or remeasuring wire to obtain missed information, can be costly to a customer.
Another problem associated with these prior art machines and the manual method of recording information is that the splice locations recorded by the operator do not correlate with the order and location of the splices in the rewound wire. More specifically, the recorded locations are measured from the leading end of the wire as it comes off the first spool. Since the wire is rewound on a second spool, the trailing end of the wire becomes the leading end of the wire as the wire comes off the second spool. Accordingly, the recorded splice locations are in reverse order. In order to correct this problem, the operator must either recalculate the locations of the splices from the trailing end of the wire, or rewind the wire on the first spool. Unfortunately, both methods are undesirable. A substantial amount of operator time is required to recalculate the splice locations and the results are subject to error. Rewinding the wire onto the other spool also requires additional operator time as well as tying up the machine, which instead could be used to measure and inspect another spool of wire.
As will be readily appreciated from the foregoing discussion, there has developed a need for measuring the total length of electrical wire on a spool, as well as accurately detecting and locating each splice in the wire and generating this information in a data form that is easily stored and retrieved for later use by a customer. Further, there is a need to provide this information in a form that corresponds to the splice locations in wire rewound on another spool such that the leading and trailing ends of the wire are reversed. This invention is directed to an improved method and apparatus for inspecting electrical wire as it is unwound from a wire spool and rewound onto another wire spool, and providing wire length and splice related data in an easily retrievable form that corresponds to the leading end of the rewound spool of wire.